Rotary drilling bit



March 31, 1964 o. M. KlEL 3,126,913

ROTARY DRILLING BIT Filed June 23. 1961 Orhor M. Kiel INVENTOR.

ATTORNEY United States Patent 3,125,973 ROTARY DRILLDIG BIT Othar M.Kiel, Tulsa, Okla, assignor to .lersey Production Research Company, acorporation of Delaware Filed June 23, 1961, Ser. No. 11%,195 7 Claims.(til. 175378) This invention relates to a rotary drill bit. Moreparticularly, the invention relates to a drill bit of the roller conetype for use with rotary well drilling tools.

A common type of drill bit presently used in the petroleum industry todrill deep wells into the earth is the multi-cone rotary bit. This bittypically comprises three rollers cones each having a plurality ofcircumferential rows of teeth. The cone type cutters arecircumferentially spaced on the body of the bit in such a manner thatrotation of the cones on the bottom of the hole will cut the underlyingformation. During rotation, the drilling force exerted on the bit isconcentrated on the ends of the wedge-shaped teeth which contact theearth formation to cause a chipping away of the earth and thereby form ahole or well. The chipped portions of the earth are carried away by thecirculation of drilling fluid which is pumped from the surface throughhollow drill pipe, to the top of the well where the portions are removedfrom the drilling fluid. The drilling fluid in addition to transportingthe cuttings also cleans and cools the cutters.

The circumferential rows of teeth formed on the cutters are spaced apartand are often olfset relative to the rows on adjacent cutters so as notto interfere with the rotation of the cones, and to make substantiallycomplete contact with the bottom of a Well.

An over-all object of this invention is to provide a drill bit for useinthe rotary drilling of wells which has increased efiiciency and bitlife.

Another object of this invention is to provide a conetype drill bit forthe rotary drilling of Wells wherein the cones are non-circular andcapable of imparting a vibratory effect to the drill bit and therebyincrease its penetration efiiciency.

Another specific object of this invention is to provide a rotating conetype drill bit wherein the outer row of teeth (i.e. the heel teeth) on aconical cutter element defines a non-circular periphery, and wherein theinner rows of teeth on each cone define a circular periphery. The outerrow provides a vibrating effect on the drill bit as it is rotatedagainst the earth while the inner rows serve to stabilize and maintainthe drill bit on a straight drilling path.

These and other objects and a better understanding of this invention maybe had by referring to the following description and claims taken inconjunction with the following illustrations, of which:

FIGURE 1 is a perspective view of a drilling bit having tri-cone cuttingelements which is contemplated to be the best mode of practicing thisinvention.

FIGURE 2 is a bottom view of the tri-cone drilling bit of FIGURE 1 whichshows the cutting face exposed to a formation being drilled.

FIGURE 3 is a plan view looking axially of a single cone to show thenon-circular arrangement of the outer row of teeth as taught by thisinvention.

Referring now to the drawings and in particular to FIGURES 1 and 2, atypical rotary drill bit improved in accordance with this invention isindicated generally by the numeral Ill. The drill bit It) is normallysupported by a threaded portion 12 to a drill stem (not shown) whichextends to the surface of the earth where rotary motion is imparted tothe drill bit Itl. Drill bit It) includes three equally spacedcircumferential conical cutters 14, 14'

Patented Mar. 31, I964 and 14"each rotatably supported and journalledwithin the downwardly projecting body or legs 16.

Each of the conical cutters is integrally formed with circumferentialrows of wedge-shaped teeth 17 designated as inner rows 18 and 19 and anouter row 20. In a typical rotary drill bit, the circumferential rows ofteeth 18, 19 and 2% are formed so that a curve drawn through the outertips of the teeth 17 of each row in a plane perpendicular to the axisaround which the cones 14 rotate will define a circle. Assuming circularrows of teeth, the drill bit 10 rotates substantially evenly against theformation in which a hole is being formed with very little vibration oroscillatory motion. The multiplicity of teeth 17 in each row 18, I9 and20 means that there are many teeth in continuous contact with the earth.Therefore, the drill bit Iii rotates relatively smoothly against theearth and depends primarily upon the weight established by the drillstring above the bit to chip away the hard formations encountered in oilwell drilling.

FIGURE 2 shows a bottom end view arrangement of a tri-cone drilling bit.Openings 24 provide means whereby drilling mud which is pumped downthrough the drill stem escapes from within the drill bit 10 to wash awayand carry to the surface cuttings which are chipped loose by thepressure of teeth 17 as they are rotated against the earth.

Up to this point, the description of the bit shown in the drawing hasbeen that of a conventional bit. That is, the conical cutters 14, I4 and14 are somewhat typical of many cutter structures in their arrangementand relationship of teeth which are mounted on projecting leg spindlesby means of ball bearings. This invention, then resides in a particulararrangement and relationship of the cutting teeth on each conicalcutter.

The present invention takes advantage of the observation that the rotarydrilling of wells can be greatly enhanced through the application ofvibratory or percussion energy to a rotating bit. Past charts to exploitthis observation have entailed the attachment of expensive andcomplicated devices to the drill stem above the bit. The presentinvention, however, does so in a very simple and inexpensive manner. Inparticular, the novel principle of this invention lies in the provisionof a non-circular row of teeth on each conical cutter such that avibratory or oscillatory action is imparted to the drill bit 10 so as toincrease its penetration effectiveness and over-all drilling efficiency.

The preferred arrangement of the teeth according to this invention isbest shown in the plan view of FIGURE 3. In this embodiment the innerrows of teeth 18 and 1% are circular as heretofore described. That is,curves drawn through the tips of teeth 17 in rows 18 and 19, and inplanes perpendicular to the axis about which cone I i rotates, describetwo separate circles.

The outer row 30 comprises teeth 32 and teeth 34. This outer row 3%,however, does not describe a circular configuration. That is, a curvedrawn through the tips of teeth 32 and 34 in a plane perpendicular tothe axis about which the cone rotates is non-circular. Although thisnon-circular arrangement may be of a multitude of geometricalconfigurations, it is considered the optimum embodiment to provide anelliptical arrangement where teeth 34 are of slightly less diameter(minor axis of the ellipse) than the diameter of teeth 32 (major axis).This is emphasized by dotted line 36 which would be the curve formed bythe teeth 32 in the outer row if all of the teeth 32 and 34 were ofequal diameter. It should be noted that the minor and major axes, ormore generally the axes of the non-circular shape, whatever it may be,shall preferably intersect at a point which coincides with the conicalcutter axis.

The embodiment illustrated in FIGURE 3 represents a typical conicalcutter constructed in accordance with this invention for use in aconical multi-cutter drill bit.

In operation, the non-circular arrangement of the outer row of heelteeth on each conical cutter causes a vibratory or reciprocating motionof a drill bit as it is rotated during the drilling of a hole. Toillustrate this feature of the present bit, it is first noted that as aconventional bit rotates on the bottom of a hole, the bottom remainsesscentially fiat. With the new hit, however, elliptical cutters tend toproduce a sinusoidal or wavy configuration on the bottom of a hole. Asdrilling continues, high portions of the elliptical cutters come intocontact with high portions of the sinusoidal configuration on the bottomof the hole. This results in a sharp upthrust or vibration to the drillstring. Teeth on adjacent cutters are lifted from the bottom of the holeand thereby leave the rock close to the point of impact less supported.Conversely, as low points of the elliptical cutters encounter lowportions of the sinusoidal configuration, the adjacent circular cuttersare dropped on the bottom of the hole. Since the portions of the holeadjacent to the resulting impacts (on the low portions of the ellipticalcutter paths) are unconfined, larger than normal chips are produced withless expenditure of energy.

The vibratory motion engendered by the invention markedly increases theeffectiveness of a bit to chip away hard formations which areencountered in drilling. The greatest volume of rock which must bechipped loose in any given borehole lies adjacent the circumference ofthe hole, and it is this particular are which is contacted by the outerrow of teeth 30. The non-circular arrangement of this row of teethpermits the bit weight to be especially concentrated where the mostdifiicult drilling occurs.

In one test of the invention, the outer rows of worn cutting teeth on an8% inch diameter tri-cone rotary drill bit were rebuilt to form theconfiguration of FIGURE 3, i.e., having an over-all elliptical shape. Inthis experiment, the difference between the major and minor axes of theouter row of teeth on each cone was about of an inch. The inner rows ofteeth were maintained circular to allow the bit to turn freely andimpart a directional effect to the drilling operation.

The above bit drilled two hundred and forty feet (240') of hole inapproximately three and one-half hours. Records indicate that otherwells drilled in the same area through the same formation usingidentical-type bits (but lacking the non-circular profile) requiredapproximately seven and one-half hours to attain the same depth ofdrilled hole. Examination of the chips of earth returned to the surfaceby the drilling mud indicated that the elliptical arrangement of theouter row of teeth of the test bit produced chips of earth formationapproximately ten times the size of the rock chips removed when aconventional drill bit was used. It was also observed that the drillstem appeared to be moving up and down approximately of an inch.

The arrangement of a conical cutter as shown in FIG- URE 3 wherein theinner rows of teeth 18 and 19 are maintained circular and the outer rowof teeth 3% is noncircular or elliptical, is considered the preferredembodiment of the invention. This embodiment is not to be taken,however, as a limitation of the invention, but is merely exemplary ofthe application of the principles of the invenion. An additionalembodiment which suggests itself is that of providing non-circular teethon one or more of the inner circumferential rows 18 or 19 and retainingthe outer row 30 circular to impart directiveness. Other embodimentsinclude various geometrical non-circular ara Larangements other thanelliptical of the outer row of teeth 30. One such arrangement includesan outer row configuration whereby there are four peripheral lengths oflongler teeth interspaced with peripheral lengths of shorter teetAlthough this invention has been described with a certain degree ofparticularity, it is manifest that many changs may be made in thedetails of construction and the arran ement of components withoutdeparting from the spirit and scope of the appended claims.

What is claimed is:

1. A drill bit for the rotary drilling of wells comprising a body; amultiplicity of conical cutters rotatably supported by said body, aplurality of rows of teeth integral with each said cutter, at least oneof said rows having teeth of unequal length with teeth of equal lengthdisposed about apart to impart percussion motion to said bit during saiddrilling.

2. A drill bit for the rotary drilling of wells including a body, amultiplicity of conical cutters rotatably supported on said body, aplurality of rows of teeth integral with each cutter, the improvementcomprising at least one of said rows having teeth of unequal length,said row being divided into four portions, the teeth in each separateportion being of equal length, the teeth in adjacent portions being ofunequal length whereby to impart percussive motion to said hit uponrotation thereof during drilling.

3. A drill bit for the rotary drilling of a well in an earth formationcomprising a body attachable at its upper end to a rotary drillingstring; a multiplicity of conical cutters, each such cutter having anaxis that is rotatably supported by said body at the lower end thereofto contact said formation; a plurality of rows of teethcircumferentially formed on each said cutter, said rows including anouter row of heel teeth on each cutter; the heel teeth on one peripheralportion of the outer row of each cutter having a radius from the axis ofsaid cutter which is less than the radius of the heel teeth on anotherperipheral portion of the same outer row.

4. A drill bit of the type defined in claim 3, wherein the heel teeth oneach said cutter define an elliptical circumferential shape with eachaxis of the ellipse intersecting the axis of its respective cutter.

5. A drill bit for the rotary drilling of wells comprising a body, aplurality of conical cutters rotatably supported and journalled withinsaid body, a plurality of rows of teeth circumferentially and integrallyformed on each said cutter, the outer row of teeth on each said cuttercomprising heel teeth varying in length around said cutter to define anoncircular periphery, at least one inner row of teeth on each saidcutter having teeth of equal length around said cutter to define acircular periphery.

6. A drill bit as defined in claim 5 in which the heel teeth in theouter row on each cutter vary in length so as to define an ellipticalperiphery.

7. A drill as defined in claim 5 in which the outer row of teeth on eachcutter has four peripheral intervals of longer teeth interspaced withperipheral intervals of shorter teeth.

References Cited in the file of this patent UNITED STATES PATENTS1,796,602 Hull Mar. 17, 1931 1,840,390 Failing Jan. 12, 1932 2,061,650Catland Nov. 24, 1936 2,533,259 Woods et al Dec. 12, 1950

1. A DRILL BIT FOR THE ROTARY DRILLING OF WELLS COMPRISING A BODY; AMULTIPLICITY OF CONICAL CUTTERS ROTATABLE SUPPORTED BY SAID BODY, APLURALITY OF ROWS OF TEETH INTEGRAL WITH EACH SAID CUTTER, AT LEAST ONEOF SAID ROWS HAVING TEETH OF UNEQUAL LENGTH WITH TEETH OF EQUAL LENGTHDISPOSED ABOUT 180* APART TO IMPART PERCUSSION MOTION TO SAID BIT DURINGSAID DRILLING.